Delay fuse compositions



Oct. 31, 1961 Filed May 5, 1959 AVERAGE BURNING TIME IN SECONDS D. T. ZEBREE 3,006,748

DELAY FUSE COMPOSITIONS 2 Sheets-Sheet 1 l I I l I I I I CURVES A 8I B, Bu O 8I Te EACH I-74 MI CRONS I o FAILURE ENCOUHTERED B|q O Te\ A AT 49/51 .FAILURE I IA,AMBIENT RIOOM TEMP.

l l I ENCOUNTERED -AT 82/l8 3 FAILURE ENCOUNTERED I -'65Fs -FAILURE ENCOUNTER? AMBIENT R QOM TEMP. r l

AT 82/l8 I'AILURE L ENCOUNTERED 'FAILURE ENCOUNTERED CURVES C8D, B 0 l-ZO MICRONS, Te [-74 MICRONS 0 I0 so so so Te I00 90 so To 60 50 4o 30% Ba 0 FUSE POWDER COMPOSITION,WE|GHT BASIS FIG. I

DAVID T. ZEBREE INVENTOR.

BY MgPM AGENT Oct. 31, 1961 Filed May 5, 1959 AVERAGE BURNING TIME IN SECONDS D. T. ZEBREE DELAY FUSE COMPOSITIONS 2 Sheets-Sheet 2 CURVES E 8 F B O I-74 MICRONS Te=5-4O MICRONS AMBIENT ROOM TEM.

B00 Se MBIENT ROOM TEMF? CURVE G Bu 0 8 Se I-74 MICRONS CURVE H Bcl =I-2O MICRONS, Se Hr-74 MICRONS Te OR Se so Ba 0 0 IO 20 3O 4O 5O 60 I00 8O 7O 6O 5O 4O FUSE POWDER COMPOSITION, WEIGHT BASIS FIG. 2

DAVID T. ZEBREE INVENTOR.

BY Mg. (PM

AGENT re rates are f? r n h Patented Oct. 31, 1951 8 Claims. (Cl. 522) This invention relates to barium peroxide-tellurium delay fuse compositions wherein the range of ingredient proportions in which tellurium is operable is extended. In another aspect this invention relates to barium peroxide-tellurium delay fuse compositions characterized by shortened burning times which are variable as a function of particle size of at least one of the barium peroxide and tellurium ingredients. In another aspect this invention relates to a method in accordance with which burning time of barium peroxide-tellurium delay fuse mixtures, shorter than heretofore, is obtained as a function of particle size of one or both the barium peroxide and tellurium ingredients. In another aspect this invention relates to a method in accordance with which the range of operability of tellurium in barium peroxidetellurium delay fuse mixtures is extended as a function of particle size of one or boththe bariumperoxideaand;

tellurium ingredients. in still another aspect this invention relates to delay blasting caps containing barium peroxide-tellurium delay fuse compositions, wherein the range of proportions in which the tellurium ingredient is operable is broader than heretofore and wherein for any specific ingredient proportions the burning time is lowered and is variable within a range of such lowered values as a function of particle size of at least one of the barium peroxide and tellurium ingredients.

Delay fuse compositions are applied in numerous applications as media through which an explosive or defiagrating material is initiated in order to provide a desired delay between the initial firing and initiation of the basic charge. Thus, in the blasting cap art, a delay elec tric blasting cap contains generally a base charge of a detonatable explosive such as pentaerythritol tetranitrate (PETN), a heat-sensitive primer charge such as diazodinitrophenol superposed on the base charge and adapted to detonate the base charge by its own detonation, an ignition charge above the primer, and a delay fuse disposed between the ignition and primer charges. The delay fuse ignited by combustion of the ignition charge exhibits a rate of burning such that a specified time interval lapses between initiation of the ignition and primer charges. Squibs as a flame-producing means are similar to detonator caps and can utilize delay fuse compositions in the same manner.

As set forth in U. S. Re. 19,661 now expired, delay fuses comprising barium peroxide and at least one of selenium, tellurium, and sulfur have had wide use in the art for some time, not only in view of their firing characteristics, but also because they fire Without evolving any substantial amount of gas upon burning. This latter characteristic eliminates development of deleterious pressure within the cap to produce premature detonation and also eliminates development of gas pressure with bursting of the shell and concomitant failure of the shot.

Barium peroxide-tellurium delay fuse mixtures are considerably slower burning than barium peroxide-selenium delay fuse mixtures as is well known and as illustrated herein. Delay periods can, therefore, be obtained by burning barium peroxide-tellurium delay mixtures which are longer than those obtained by burning barium peroxide-selenium delay mixtures. There is a large area of burning time values intermediate those of barium peroxide-tellurium and barium peroxide-selenium mixtures which if available would provide for a markedly greater range of selection of burning times. Further, the range of ingredient proportions in which tellurium and barium peroxide-tellurium delay fuse compositions is operable is much shorter than for barium peroxide-selenium fuse mixtures so that to extend the operability of tellurium L n n weuid censuse be advantageouse We This invention is concerned with barium peroxide-tellurium delay fuse mixtures which exhibit burning times shorter than those heretofore obtainable to thereby broaden the range of available burning times from such mixtures. The invention is further concerned with such delay fuse mixtures wherein the range of ingredient proportions in which tellurium is operable, is extended. Selenium, substantially gray metallic-like, can be utilized as an ingredient of the delay fuse compositions of this invention, when desired.

An object of the invention is to provide new barium peroxide-tellurium fuse mixtures which are characterized by shortened burning times to provide, therefore, for a broadened range of available delay periods for barium peroxide fuse mixtures. Another object is to .provide for an extension of operability of tellurium in those barium peroxide-tellurium delay fuse mixtures having shortened burning times, above described. Another object is to provide amethod .fcmQbtaL Qgashortenedabmning times for barium peroxide-tellurium delay fuse mixtures. Another object is to provide method for extending the operability of tellurium in barium peroxide-tellurium delay fuse mixtures having shortened burning times, above described. Other objects and aspects will be apparent from the accompanying disclosure and the appended claims.

In accordance with the invention barium peroxidetellurium delay fuse compositions are provided in which the particle size of at least one of the said barium peroxide and tellurium components is below about 50 microns, whereby the range of component proportions of said compositions in which tellurium is operable is extended, and burning time is faster than heretofore and is variable as a function of said particle size. Further, in accordance with the invention, a shortened delay period, in firing a delay blasting cap containing a barium peroxidetellurium mixture as a delay fuse, is obtained by burning as said fuse one in which the particle size of at least one of the barium peroxide and tellurium components is not greater than about 50' microns.

Further, in accordance with the invention, the range of component proportions of barium peroxide-tellurium delay fuse compositions in which the tellurium component is operable is extended by maintaining the particle size of at least one of the barium peroxide and tellurium components below 50 microns. Still in accordance with the invention, delay blasting caps are proided which contain a barium peroxide-tellurium delay fuse wherein the particle size of at least one of the barium peroxide and tellurium components is not greater than about 50 microns whereby a broadened range of delay periods of such fuse compositions is provided, and the range of component proportions within which tellurium is operable, is extended.

When desired, selenium can be utilized as a component of the delay fuse compositions Without impairing the function of the limited particle size of the barium peroxide and tellurium components.

The invention is illustrated with reference to the curves of FIGURES 1 and 2 which provide comparative data obtained from firing tests utilizing barium peroxide-tellurium delay fuse mixtures both of the prior and of the invention. With reference to FIGURE 1 are shown curves (A) and (B) which summarize results obtained when firing delay blasting caps containing barium peroxide-tellurium delay fuse mixtures of the prior art. As

shown by curve (A), some failures were encountered in all trials at -65 F. where as at ambient room temperatures firings with the same ingredient proportions were sucessful, the tellurium component being operable in a content range of from 18-40 percent. Curves (C) and (D) illustrate the results of firing tests made for the same mixtures except that the particle size of one of the ingredients, i.e., barium peroxide, was reduced to within a range of 120 microns. As shown by a comparison of curves (C) and (D) with (A) and (B), the mixture was operable at 65 F. and at ambient room temperature delay time was not only faster but the maximum of the range of operability was extended from 40 percent tellurium to 50 percent. Further, burning times were markedly reduced as, for example, from 31 secs. (curve (B)) to 13 secs. (curve (B)).

A comparison of (A) and (B) of FIGURE 1 with curves (E) and (F) of FIGURE 2. illustrates the effect of reduced particle size of the tellurium component on burning time of barium peroxide-tellurium delay fuse mixtures. Thus, curve (B) illustrates the same effect shown by curve (C) of FIGURE 1, namely, that by re duction in particle size of at least one of the fuse mixture components, operability is obtained at extremely low temperatures, under which conditions the mixture employing prior art barium peroxide-tellurium fuse mixtures is inoperable. Also, at ambient room temperatures, the burning times are markedly faster, as shown by curve (F). Thus, at 20 percent tellurium the composition containing the prior art delay fuse mixture has a burning time of 31 secs. (curve (B)) whereas the mixture containing tellurium of reduced particle size, at the same tellurium content (curve (F has a burning time of 17.5 secs. Further, as shown by curve (F) the tellurium at ambient room temperatures is operable over a range up to at least 60 percent.

As illustrated with reference to curves (G) and (H) of FIGURE 2 the effect of reduced particle size of barium peroxide-selenium delay fuse mixtures is slight at most. Thus, curve (G) illustrates the results from firing tests utilizing barium peroxide-selenium delay fuse mixtures in which the particle size of the barium peroxide and selenium components is each l74 microns, and curve (H) illustrates the same firings repeated except that the particle size of barium peroxide ingredient is reduced to about l-20 microns. The small differences in burning time are clearly set forth by these curves.

The data of Tables I and II, following, further demon strate the effect of ingredient particle size, on burning time, of barium peroxide-tellurium delay mixtures alone and containing selenium. The tabulations show that as particle size of the barium peroxide and telluiium components is decreased, burning time of the delay composition is decreased. The presence of selenium as brought out by the tables, does not in any manner alter the effect of reduced particle size of barium peroxide and tellurium components on burning characteristics of the fuse composition.

1 Unseparated. 1-74 microns.

The following tabulation illustrates effect of both reduced particle size of BaO and tellurium.

Table II Wt. Percent Particle Size, Avg. Burning Microns Time, Sec.

Trials Each BaO; Te Se Ba Te Room 65 F.

Temp.

40 20 5-30 1 Control 1O 18. l 20. 6 40 20 5-20 1 Control 16. 2 18. 5 40 5-30 540 10 15. 7 17. 2 40 20 5-20 540 10 14. 6 16. 1 5-30 1 Control 10 8. 8 11. 4 30 5-30 5-40 10 7. 8 10. 0

1 Unseparated 1-74.

All firing tests reported in FIGURES 1 and 2 were made utilizing a delay electric blasting cap formed from a 4" x copper shell containing a base charge of 0.40 gram pentaerythritol tetranitrate pressed in the bottom of the shell, a primer charge of 0.30 gram diazodinitrophenol pressed on top the base charge, 2.4 grams of the delay fuse mixture supported as a core 2 in length and filling a lead tube on top of the primer, 0.65 gram of a Pb-Se (substantially stoichiometric proportions) ignition powder superposed on the lead tube, a sulfur ignition plug over the said ignition mixture, 8. charge of asphalt waterproofing on top the said ignition plug, a sulfur topping above the said Waterproofing, and leg wires connecting with a bridge wire disposed within the said ignition mixture. The caps were then fired. Caps reported in Tables I and II were made up similarly to those in FIGS. 1 and 2 except in these tables the fuse core was 1.5 in. long.

As illustrated with reference to the data of FIGURES 1 and 2 and Tables I and II, this invention is based on the discovery, in delay fuse mixtures, that barium peroxide and tellurium of particle size within a range below about 74 microns, as components of barium peroxidetellurium delay fuse compositions impart unpredioted burning time and operability characteristics.

Although it is within the scope of the invention to utilize the barium peroxide and tellurium components of particle size below about 74 microns, values not greater than about 50 microns are preferred in order to provide a significant extension of tellurium operability and suitable degree of reduction in burning time. Thus, in the preparation of components for the compositions of this invention, the available barium peroxide and/ or tellurium fractions, i.e., unseparated fractions are fractionated to remove a predetermined proportion of the larger particles to provide the resulting finer particles for use in the practice of the invention. Generally, the preferred particle size for both barium peroxide and tellurium is in the range of about l-50 microns, a maximum particle size up to about microns being often utilized and a minimum of 5 microns being generally preferred inasmuch as when significant proportions of the finer particles are employed, problems are presented in respect of flowability during handling of the mixtures such as during the manufacture of the detonating device or delay fuse unit.

Proportions of ingredients employed in the compositions of the invention are inclusive of those heretofore utilized in the prior art barium peroxide-tellurium delay fuse mixtures which have been generally in the order of about 60-80 percent barium peroxide and 2040 percent tellurium.

However, as illustrated with reference to curves (C) and (D) of FIGURE 1, the ranges are somewhat broader in the practice of this invention, such as from about 86 percent barium peroxide and about 14-50 percent tellurium (curve (B)) when utilizing a barium peroxide component of l-20 microns. Similarly, as shown by FIGURE 2, curve (F), the contents of barium peroxide and of tellurium are 40-80 and 20-60 percent, respectively, when tellurium of particle size is Within the range of 540 microns. Accordingly, although the exact limitation as to range of operability is dependent upon the particle size of the components, the compositions of this invention are generally operable in a range of from about 40-86 percent barium peroxide and 14-60 percent tellurium. When selenium is employed, barium peroxide and tellurium ratios can remain in the same proportion with the selenium content of the mixture generally not exceeding about 25 percent.

An exemplary blasting cap arrangement employed in the practice of the invention comprises an elongated metal shell closed at one end and containing a suitable base charge, in the bottom, such as PETN with a suitable primer charge such as straight diazodinitrophenol superposed on the base charge. A barium peroxide-tellurium delay fuse mixture of the invention, as a core in a lead tube, is superposed, coaxially with the shell, on the primer charge. Lead wires connected with an outside power source extend into the shell through the open end and terminate in close proximity to the delay fuse. A bridge or resistance wire connects the terminating ends of the lead wires and is disposed in relation with an ignition composition to cause ignition of same by heat from passage of the electric current through the resistance wire, the ignition mixture being disposed above the delay fuse to ignite it in response to its own ignition. Exemplary ignition compositions are loose lead-selenium powder or suitable matchhead type compositions. Conventional sealing means is provided for closing the shell end containing the lead wires such as by employing a conventional phenolic or sulfur type ignition plug closure with waterproofingimaterial-aboveiitinzmsuit Firing is then accomplished by passage of electric current through the bridgewire and ignition of the ignition mixture. Detonation is then accomplished following the time required for burning the delay fuse. Series firing is accomplished by connecting a plurality of such delay assemblies, each selected to fire at the end of a predetermined period of time, consonant with methods well known in the art.

As will be evident to those skilled in the art, various modifications can be made or followed, in the light of the foregoing disclosure and discussion, without departing from the spirit or scope of the disclosure or from the scope of the claims.

What I claim and desire to protect by Letters Patent is:

1. A blasting cap delay fuse composition consisting essentially of from 40-86 weight percent barium peroxide and from 14-60 weight percent tellurium, and the particle size of at least one of the said ingredients being respectively within the range of from 1-20 microns and 5-40 microns.

2. A blasting cap delay fuse composition consisting essentially of barium peroxide, tellurium, and selenium, and containing said barium peroxide in a weight ratio to said tellurium in the range of from 86:14 to 40:60, and containing said selenium in an amount up to about 25 weight percent; and the particle size of at least one of the said barium peroxide and tellurium ingredients being respectively Within the range of from 1-20 microns and 5-40 microns.

3. In the detonation of a delay blasting cap containing barium peroxide-tellurium as the delay fuse, the improve ment which comprises burning as said fuse one which consists essentially of from 40-86 weight percent barium peroxide and from 14-60 weight percent tellurium, and wherein the particle size of at least one of said barium peroxide and tellurium is respectively within the range of from 1-20 and 5-40 microns.

4. In the detonation of a delay blasting cap containing a barium peroxide-tellurium mixture as the delay fuse, the improvement which comprises burning as said fuse one consisting essentially of barium peroxide, tellurium and selenium, and containing said barium peroxide in a weight ratio to said tellurium in the range of from 86:14 to 40:60, and containing said selenium in an amount up to about 25 Weight percent; and the particle size of at least one of the said barium peroxide and tellurium ingredients being respectively within the range of from 1-20 microns and 5-40 microns.

5. In a blasting cap consisting essentially of a delay fuse together with means for initiating burning of said delay fuse and a charge adapted to be initiated subsequent to burning of said fuse by heat from said burning, the improvement comprising as said delay fuse from 40-86 weight percent barium peroxide and from 14-60 weight percent tellurium, and the particle size of at least one of the said ingredients being respectively within the range of from 1-20 microns and 5-40 microns.

6. In a blasting cap consisting essentially of a delay fuse together with means for initiating burning of said esllLfuri-sealnm ldelayn fuseiandiancharge, adaptediolaeninitiated subse-a quent to burning of said fuse by heat from said burning, the improvement comprising as said delay fuse a composition consisting essentially of barium peroxide, tellurium and selenium, and containing said barium peroxide in a weight ratio to said tellurium in the range of from 86: 14 to 40:60, and containing said selenium in an amount up to about 25 weight percent; and the particle size of at least one of the said barium peroxide and tellurium ingredients being respectively within the range of from 1-20 microns and 5-40 microns.

7. A composition of claim 1 wherein the particle size of said barium peroxide component is within the range of from 1 to 20 microns and the particle size of said tellurium is from 1 to 74 microns.

8. A composition of claim 1 wherein the particle size of said tellurium component is within the range of from 5 to 40 microns and the particle size of said barium peroxide is from 1 to 74 microns.

References Cited in the file of this patent UNITED STATES PATENTS 

1. A BLASTING CAP DELAY FUSE COMPOSITION CONSISTING ESSENTIALLY OF FROM 40-86 WEIGHT PERCENT BARIUM PEROXIDE AND FROM 14-60 WEIGHT PERCENT TELLURIUM, AND THE PARTICLE SIZE OF AT LEAST ONE OF THE SAID INGREDIENTS BEING RE- 